Infestation of conifers by insect pests of the beetle family Scolytidae is well documented. Insect attacks on healthy, damaged, or weakened host trees continue to be a significant commercial and ecological problem. Trees that are susceptible to infestation by scolytids include loblolly pines, eastern and western white pines, eastern and western yellow pines, Norway spruce, larch, eastern redcedar, eastern hemlock, Fraser fir, Douglas fir, and other fir trees.
Certain chemical insecticides have been employed for limited protection of trees. However, the use of synthetic chemical insecticides in insect control raises serious concerns about the adverse environmental and ecological effects these agents may have. Often, organic pesticides are more costly than naturally occurring products and the effective control of insects by means of an insecticidal agent typically requires relatively extensive application of the insecticide to targeted susceptible surfaces of the host tree. Because insecticides are generally nonspecific in their toxicity and are typically applied by broadcast application, e.g. aerial or high power sprayers, their use is associated with a significant risk of harm to non-target organisms, such as natural enemies of scolytids, as well as bees and other pollinators. Chlorpyrifos for example is a registered insecticidal compound used in scolytid control that has a longer residual impact on natural enemies of scolytids than on scolytids.
In an effort to avoid the use of insecticides, researchers have devoted considerable attention to the development of cost-effective repellents derived from naturally occurring products for the control of scolytid infestations. As a result, they have developed both chemical and microbial agents capable of keeping pests from harming a plant by either repelling or attacking the pests, pesticides.
For instance, U.S. Pat. Nos. 5,403,863, 5,518,757 and 5,695,807, which are incorporated by reference herein, disclose methods for repelling scolytids using the scolytid-repelling compound 4-allylanisole or a selected analog (anisole, allylbenzene, 4-isopropylanisole, p-anisaldehyde, ethylbenzene, cumene or 4-methoxyacetophenone), and mixtures thereof. 4-allylanisole is a naturally occurring compound found in the resin exuded by a potential host tree susceptible to infestation by scolytids. An important advantage to the use of 4-allylanisole or its analogs in scolytid control is that effective protection may be obtained without spraying all surfaces. Scolytid control may be achieved by applying the compound directly as a concentrated liquid, powder, or vapor to a portion of the tree to be protected. Because it does not require uniform application, pesticides such as those disclosed in this family of patents and applications may be applied in a packaged delivery container, such as a pre-filled projectile (e.g., a so-called "paint ball," although it should be appreciated that any container that emits the contents upon contact--even if not released for free flight or otherwise restrained--should be considered a projectile for purposes of this application) which delivers the desired compound by emission after contacting a portion of the tree (which will, for convenience, be termed an "explosion" although it need not be a sudden and instantaneous discharge). In this way, a pesticide, can be applied at a high enough level on the tree--which may exceed 50 feet--for proper effectiveness; in the case of those pesticides disclosed herein, such heights may be in the range of 2-3 feet to 20-30 feet, as appropriate for the pest and the pesticide, which will be easily determinable by those skilled in the art based upon the pest to be targeted. Also, the repellent compound may be carried on elution devices placed proximate to the tree. The repellent compound may be impregnated in a polymer mass, such as by being encased in a suitable polymer for delivery as a pre-filled projectile, or microencapsulated in a suitable polymer. The repellent compound could be delivered onto or in proximity with a surface to be protected by placing the polymer mass or the microencapsulated repellent in proximity with the surface.
There is a need to develop alternative scolytid repellents to those currently in use.